Shadow mask bimetal strip means with motion-limiting bumper



Aug. 18,1970 J. w. COOPER ETAL 3,

SHADOW MASK IN BIMETAL STRIP MEANS WITH MOTION-LIMITING BUMPER Filed Oct. 5, 1967 L INVENTJORSJ JOSEPH W. COOPER LASZLO JAVORIK -fl ,g

ATT YS FIG.4

United States Patent U51. Cl. 313-85 3 Claims ABSTRACT OF THE DISCLOSURE In a three-point suspension system for an apertured shadow mask in a color kinescope, the top mounting spring is cantilevered axially of the tube from a bimetal supporting bridge which is bracketed to the frame of the mask. The top spring defines an aperture for'receiving a mounting stud embedded in the peripheral flange of the faceplate panel, and the bases of two U-shaped bumpers are attached to the mask on either side of the aperture of the top spring so that the upwardly-projecting legs of the bumpers extend alongside of the spring. The bumpers prevent deformation of the bimetal support when the faceplate receives a shock by limiting the lateral displacement of the mounting spring relative to the mask while permitting longitudinal bending and translation of the spring.

BACKGROUND The present invention relates to a color television kinescope; more particularly, it pertains to a three-point system for suspending an apertured shadow mask within the faceplate panel of a conventional color television kinescope.

In conventional color television kinescopes, an apertured shadow mask is suspended within the faceplate panel of a cathode ray tube or kinescope, and each of the apertures of the shadow mask is associated with a triad of phosphor dots deposited on the screen of the faceplate panel. Each of the three dots associated with one aperture emits a different color (red, blue, and green) of light in response to an impinging electron beam. The three beams are generated in the constricted neck portion of the tube, and each beam is modulated with a video signal representative of its respective color component of the overall image being reproduced.

As the beams scan the viewing area in a raster, they alternately impinge on the metallic shadow mask and the screen by passing through the apertures for selectively scintillating their associated phosphor dots. After a warm up time, the beams impinging on the shadow mask heat the mask which reaches an equilibrium temperature of 20-30 C. above the equilibrium temperature of the faceplate panel. Thus, the mask expands radially of the tube (the axis of the tube being defined as a line which passes through the axis of the constricted neck portion and the center of the viewing area); and the apertures of the shadow mask move out of alignment with their associated triad of phosphor dots causing color dilution.

This eifect increases progressively with the distance from the center of the viewing area, and thus, it is more pronounced in the fringe areas.

One important method of correcting for this misregistration as the shadow mask heats up is to provide bimetallic supports for each of the flat steel springs which mount the shadow mask to studs embedded in the faceplate panel. These bimetal supports are designed so that as the temperature of the shadow mask rises, the mask will be shifted bodily toward the screen and thus, the apertures will be brought back into alignment with their associated triads of phosphor dots.

3,524,972 Patented Aug. 18, 1970 This system for correcting for misregistration by using bimetals in the suspension system for the shadow mask is disclosed in the co-pending, co -owned application of Schwartz and Javorik for Suspension System. for Color Television Tube Mask, S.N. 559,623, filed June 22, 1966. It has been found that although this suspension system operates satisfactorily from the standpoint of correcting for misregistration in response to heating of the shadow mask, permanent damage can be caused to the bimetallic supports from which the mounting tabs or springs extend to receive the mounting studs. The most serious threat of damage occurs when the faceplate panel receives a shock laterally of the screen. Such a shock may be imparted by dropping the tube.

The shadow mask assembly, being made of metal and secured to a relatively massive frame, has enough inertia to permanently damage the bimetal supports in the top mounting spring since the mounting stud embedded in the faceplate panel holds one end of the spring from lateral movement whereas the other end is fastened to the bimetal supporting bridge. Thus, a bending moment is transmitted directly from the mounting stud through the mounting spring and to the bimetal supporting bridge. Efforts to prevent this damage to the bimetal supporting bridge are complicated by the fact that the mounting spring must be allowed to move axially of the shadow mask in order to correct for misregistration. Further, it must also be possible to easily depress the mounting spring (i.e. bend it longitudinally of itself) to remove the same from its associated mounting stud. The reason for the latter requirement is that during the photographic deposition of the various phosphor patterns on the screen, it is required that the mask be removed and inserted a number of times while an emulsion is exposed to actinic light. The light passes through the shadow mask apertures and impinges on polyvinyl alcohol mixed with potassium dichromate to cross link the two and produce unsoluable dots for carrying the phosphor.

SUMMARY The present invention seeks to overcome the problem of transmitting a shock force through the bimetal supporting bridge of the top mounting spring in a threepoint suspension system for a shadow mask. In a preferred embodiment, U-shaped bumpers are mounted on either side of the mounting spring or tab adjacent to the aperture which receives the stud embedded in the flange of the faceplate panel thus defining four upstanding posts for preventing lateral motion of the spring.

With this arrangement, any lateral force which is transmitted from the faceplate panel to the mask at this mounting location is transmitted directly from the mounting stud to the bumpers and then to the mask frame. Thus, the force is not permitted to be transmitted through the bimetal supporting bridge for the mounting spring, and at the same time, the mounting spring is permitted to move longitudinally of itself (i.e. axially of the shadow mask) in correcting for misregistration. Further, the spring may easily be depressed to facilitate removal of the shadow mask from the faceplate panel during the phosphor deposition. Other featuresand advantages of the instant invention will be obvious to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing in which identical reference numerals will refer to like elements in the various views.

shadow mask if a color kinescope incorporating features of the present inventlon;

3 FIGS. 2-3 illustrate the inventive mounting assembly of FIG. 1; and

FIGS. 4-5, show alternative embodiments of the inventive assembly.

DETAILED DESCRIPTION In FIG. 1 there is seen a rear view of a shadow mask mounted within a faceplate panel for a color kinescope. That is, the view is as would be seen from the constricted neck portion in which the source of electron beams is located, with the neck and the funnel of the tube removed. In FIG. 1, the apertured shadow mask is generally designated 10, and it is attached to a frame 11 which is mounted to a flange 12 of the faceplate panel at three locations. The two side mounting locations are generally designated 13, and the top mounting location is generally designated 14.

Each of the side mounting arrangements are those which were disclosed in the above-identified, co-pending application of Schwartz and Iavorik. These mounting means form no part of the instant invention; and they will not, therefore, be described in great detail. However, it is noted that the side suspension means 13 do include a bimetal support for a fiat steel spring 16 which receive the mounting studs 17 embedded in the faceplate panel flange 12; and that these mounting means are adapted to correct for misregistration of the shadow mask apertures with their associated triad phosphor dots when the shadow mask is heated.

It will further be noted that the top suspension means 14 is adapted to engage a center stud 18 embedded in the top of the flange 12, and that the overall suspension system comprises only three separate mounting locations, namely, one at each side and one at the top. This three-point suspension system is desirable from the viewpoint of facilitating removal of the shadow mask aperture from the faceplate panel.

Referring now to FIGS. 2 and 3, the inventive top mounting assembly is seen in greater detail. A first mounting bracket 20 is attached to the shadow mask frame 11 as by welding, and it defines a centrally-depending spacer 21. A complementary mounting bracket 22 is mounted on the other side of the stud 18; and it also defines a centrally-depending spacer 23. Attached to the spacers 21 and 23 are a first transverse bimetal rail or strip 24 and a second trnsverse bimetal strip 25. At the center of the bimetal strips 24 and 25 there is a third spacer 26 to which is attached the steel spring or tab 27 which defines an aperture 28 for receiving the stud 18.

v The above-mentioned bimetal supporting bridge for the mounting spring 27 consists of the brackets 22, the spacers 21, 23, and 26, and the bimetal rails 24 and 25. The composition of the bimetal strips 24 and 25 together with the operation of the support is set forth in more detail in the above-identified co-pending application. However, it will be noted here that in general, the bimetal strips 24 and 25 will develop an arcuate characteristic which extends toward the rear of the tube. That is, as seen in FIG. 3, the strips 24 and 25 will curve leftwardly and upwardly to move the mounting spring 27 rearwardly of the frame 11. In fact, since the mounting spring 27 is rigidly coupled to the stud 18 (at least insofar as lateral motion is concerned) the frame 11 will be moved forward of the screen as this curve or arcuate shape of the bimetal strips develop.

It is the bimetal strips 24 and 25 which are subject to permanent damage when the shadow mask is mounted within the faceplate panel and the same is jarred. For example, if the reaction force is as shown by the arrow in FIG. 3, and the mounting stud 18 is secure within the aperture 28 of the mounting spring 27, there will be a clockwise moment included in the bimetal strips 24 and 25; and if this moment is of sufficieut magnitude, it may cause permanent deformation of the bimetal strips thereby permamently twisting the mask relative to the screen and causing misregistration.

In order to prevent this damage to the bimetal support bridge, a bumper assembly, generally designated 30 is mounted in a recess 31 in the top of the frame 11. The bumper assembly 30 comprises a first U-shaped bumper 32 arranged on one side of the mounting spring 27 and adjacent the aperture 28 which receives the mounting stud 18. The U-shaped bumper 32 is formed by bending first and second depending legs or posts 33 and 34 upwardly from a bracket 30a which is secured to the frame 11. A similar U-shaped bumper 35 comprising posts 36 and 37 is formed at the opposite end of the bracket 30a, and it performs a similar function. Thus, for the particular force schematically illustrated in FIG. 3, the bumper 32 would engage the side of the metallic mounting spring 27, and the force would be transmitted through these media from the frame 11 directly to the mounting stud 18 without passing through the bimetal supporting bridge. Thus, the entire bumper assembly is formed from a single I bracket and remains integral.

With this arrangement thus described, it will be apparent that a sudden jar of the faceplate panel will not transmit a coupling moment to the bimetal support bridge for the top mounting tab in a three-point suspension system; and at the same time, the mounting spring which receives the top stud in the flange of the faceplate panel is allowed to move axially of the tube relative to the frame 11. This movement, in FIG. 3, allows for longitudinal movement of the mounting spring 27 within the channel 40 defined by the two bumpers 32 and 35. Further, the bumper arrangement allows for depression of the spring 27 within the channel 40 for removal of the shadow mask from the faceplate panel.

Turning now to FIG. 5, a first alternative embodiment is seen wherein the previously-defined brackets 20 and 22 for supporting the bimetal bridge have counterparts referenced as and 122. The mounting spring is 127.

In this embodiment, the brackets 120 and 122 are provided with extensions 125 and 126 respectively which extend centrally of the tube toward the mounting stud (118 in FIG. 3).

First and second bumpers are formed by turning up the arms or posts 128 and 129 on extension 125; and similar bumpers 130 and 131 are formed on extension 126 of bracket 120.

A second alternative is shown in FIG. 5 wherein the mounting spring is denoted 218 and the stud is denoted 228. In this case, upstanding bumpers 230 and 231 are formed out of the material of the top of the frame 211 adjacent the stud-receiving aperture 228.

Having thus described in detail a number of embodiments of the invention, it will be obvious that various structures may be substituted for that which has been disclosed while continuing to practice the principle of the invention. One such equivalent structure would be to extend the mounting spring 27 somewhat forwardly of its aperture 28 and then to form a V-shaped foot at the distal end of the spring which would be received in a corresponding aperture in the frame 11. The lateral width (that is, the dimension tranverse of the plane of the spring) of the aperture which receives the foot would be such as to prevent any lateral movement of the spring 27. It will be obvious that this kind of structure will be advantageous in preventing any coupling moment being transmitted to the bimetal strips which support the mounting spring.

Another equivalent structure would be to provide elongated slots within the mounting strip 27, for best results one on either side of the aperture 28 and extending along the longitudinal axis of the spring 27. Each of these slots, in turn, are elongated in the direction of the longitudinal axis of the spring 27; and each receives a projection or pin extending upwardly from the frame 11. The

pin has a transverse dimension a few thousandths of an inch smaller than the width of the slot. This arrangement also permits depression of the spring (in which case the apertures on the spring simply move further along the projection) and longitudinal movement of the spring relative to the spring 12 (in which case the pins ride longitudinally of their receiving apertures) which prevents twisting of the spring.

It is intended that these suggested modifications as well as other equivalent structures be covered as they are embraced within the spirit and scope of the appended claims.

We claim:

1. In a color television kinescope including a threepoint suspension system for mounting a shadow mask having a frame on studs embedded in the peripheral flange of the faceplate panel of the tube, the combination comprising bimetal strip means; means for attaching said strip means at each end to said shadow mask frame on each side of the upper center stud, said bimetal strip means extending generally parallel to the plane of said mask and deflecting at its center away from said mask when heated to urge said mask forward to correct for misregistration; a flat resilient spring member secured at one end to said bimetal strip means intermediate its ends and extending toward said'shadow mask generally parallel to the axis of said tube, the free end of said spring member being provided with an aperture for fitting over said center stud; and bumper means attached to said frame and extending outwardly thereof on both sides of and immediately adjacent to said spring to prevent twisting of said bimetal support bracket by limiting sideward motion of said spring member relative to said frame while permitting deflection of said spring member toward said frame to disengage said stud during removal of said shadow mask from said faceplate panel.

2. The structure of claim 1 wherein said bumper means comprise first and second U-shaped channel members each having a base and depending legs, said bases mounted to said mask on either side of said spring respectively and said legs extending upwardly adjacent said spring.

3. The structure of claim 2 characterized by said channel members being mounted adjacent said aperture in said spring and defining four upstanding posts for preventing twisting of said spring.

References Cited UNITED STATES PATENTS 2,942,129 6/ 1960- May. 3,330,980 7/ 1967 Shrader. 3,370,194 2/ 1968 Schwartz et al.

ROBERT SEGAL, Primary Examiner US. Cl. X.R. 313269, 288 

